Process of purifying anthracene



1 9 the crude anthracenein the proportion of 500 V Patented Nov. 25, 1 930 L cHAnLns THATGI-IER, on NEW Yam Y.

i rnoonss or runrryinez AN'rnnAcENE Ro -Drawing App1icationfi1ediune '16,

The invention relates to a process for treating crude anthracene to provlde same 111 refined condition suitable, for example, for the product on of anthraquinone by oxidation;

1 5 Anthracene for this purpose should be of high purityf-say from 85% to 95% -and "should also be in'a very finely divided state. The present invention has for itsobject a novel process of obtaining anthracene of these 10 characteristics fromfwthe' crude material, which is usually of 30%, more or less, purity and usually in the forni of comparatively large lumps 'or solid particles of an oily nature. i

i ,5 'Hereto-fore, the refining of the anthracene involved either complete solution of the crude anthracene' in some suitable solvent", or sublimation of the 1 anthracene; or both. This wasnecessa ry because it is not possihle'to rernovevsubstantially all of the: "impurities from the large solid particles ahd'lumpsfof crudejanthracene thru the agency of solvents forthe impurities, because the solvent does not of itself penetrate intothe interior of the largerparticles to extract all of their imf purities therefrom.

In accordance wlth the presentinvention,

both" of the aforesaid essential 1 characteristics of'refine'd anthracene may-be economical 1y attained Without the trouble and expense anthracenein a solvent,"

' The following illustratesthe novel jmeth od ofproviding refined anthracene from the crude material 2 V i p i 4 A suitable quantity of the crude anthraacenesayof 30 purity, more or lessfis treated in a" ball-or pebble milk-which may be solvent for substantially all of the oils and l vphenanthrene contained in the crude anthracene employed, but which will not appreciably dissolve the anthracene and carbazole.

The-grinding bytheinill is continued foi'iap ,proxiinatelyone totwo hours or until the an thracene has becomexvery finely pulverined tori sub-divided. As .asuitable solvent for this purposeeither benzol or crude coal tar solvent may be employed, and ismixed with of either subliination or of solution offthe" grindingoperation, suitably sealed with a sufficient quantity of "largerthan those crude anthracenep 1923. Serial m maeea lbs; of crude'anthraceneto from 5005 Li to 1000 lbs., of thesolvent. 1 7 Other suitable solvents may which may be mentioned carbon tetrachloride, which is particularly suitable for this purpose where fire hazards areto be strictly be used, among avoided, andwhichniay be in the proportion of 5o0'1bs. to 1000 lbs; to 500 lbs. f the anthracene. Also, mixtures of these or similar solvents rnay be used for thesainepurpose.

In the selection of solvents for this ,purpose it is to be'borne in 'I'nind that theess en tial characteristic of the invention i'sthe grindingo-f crude antharcene in a solvent for its oils andin which anthraceneitself is relatively insoluble, exceedingsaytwo parts per vent at room temperatures. Enough of the solvent should'be used in any case'to dissolvesubstantially all oft he'oils"; and two or more Thruthe sirnultaneousconibined grindi and solvent actions, re ul s are attained viltremoves the crudef'anthracene, which preclude fine grinding of such material evenwith water ina ballor: pebble jrnill; waters the; re-

65 T say to an extent not much hundred of sol were not possible in "prior practice" or I 16y nmethods; =By its actiomthesor the "greasy or oily, matters from movalof such oily Inatter, the formation of lumps of anthracene is avoided and the irn- 'pure anthracene is it maybe quicklyfbrokenup by the grinding action into extremelyffine particles; It has been found that at cene appear under 7 H obtained heretoforeonly by sublimation.

ticleof anthracene results thruithe grinding of the mixture to 'niicroscopic particles, so that substantially all of the said impurities thusyin a state suchthjat i the conclusion-of the" f the. particles of" anthra5 g the microscope-to be no Furthermor a i e I actionof the solvent'llp c mmute I i are extracted by the solvent 'duringlthis gr-ind j i ing action; and which feature is not attainedbysol vent action alone, 'as heretoforezcari r ried on, on the relatively largergparticles of '10 I successive treatnientswith solvent in the' proportion indicated may be desirableto this At the conclusion of the grinding operation and solvent action, the contents of the mill are to be discharged and filtered. The solvent is then removed by gravity or suction, and the remaining anthracene or residue washed a few times with a small portion of the solvent, or solvents, and dried with recovery of the solvents. The solvent in the filtrate may be recovered as by distillation and utilized for further operation of the process.

By the use of suitably designed apparatus, all of these operations may be performed without substantial loss of even more or less expensive solvents, such as carbon tetrachloride. When distilled, the residue or material remaining in the still consists mainly of oils and phenanathrene which may be readily separated in pure form.

If the process is conducted with anthracene of approximately 30% purity, the foregoing treatment increases the purity .of the anthracene to approximately 45%, but the same is now also in a very finely divided state, dry, and suitable for further purification treatments. By suitable selection of the solvent and control of the proportions and conditions of use thereof, as readily understood by workers in the art, substantially no anthracene or carbazole is dissolved by this refining operation, and both of these compounds remain in the resulting partly refined anthracene.

F or the removal of the carbazole from the ground and partly refined anthracene, a number of processes are available. For example, the anthracene, now containing from 40% to 50% of carbazole ordinarily, may be treated with a suitable proportion of a solvent there for, such as acetone or pyridine. One hundred parts of the former dissolves from 6 to 9 parts by weight of carbazole and from to 1 parts by weight of anthracene at ordinary factory temperatures. The latter solvent at these temperatures will dissolve from 12 to 17 parts by weight of carbazole and from 1 to 2 parts by weight of anthracene; and workers in the art wil readily understand from the figures the proper selection of proportions and establishment of conditions for the substantially complete removal of carbazole from the finely divided, partly refined anthracene.

Vhere it is desirable to avoid the use of inflammable liquids in refining operations for removal of carbazole, the same maybe removed by other well-known means such as the nitroso method described in U. S. Letters Patent No. 685,895, or by the well-known fusion with caustic alkali, producing, for ex ample, potassium carbazole and anthracene. The invention, however, is not restricted to any particular method for the separation of the carbazole from the partly refined anthracene. The crude carbazole obtained by any such suitable method, as hereinbefore set forth, may then be purified to obtain commercially pure carbazole, for example by the method described in my copending application for U. S. Letters Patent Serial No. 522,630, which has eventuated into Patent No. 1,672,630 issued June 5, 1928.

In carrying out the hereindescribed process for the refining of crude anthracene, anthracone in extremely finely divided condition and of a purity of from to is obtained. Also, the anthracene being in this condition is readily oxidized to anthraquinone without any considerable excess of oxidizing agent.

As has already been noted, there need be no loss either of anthracene or solvent thru the grinding operation, nor in the removal and purification of carbazole, as more particularly set forth in my aforesaid application. The process hereindescribed effects, therefore, economy in operation .and material, rendering it superior to those heretofore described or used for the refining of crude anthracene.

It will be understood, of course, that suit able modifications therein and additions thereto may be made without departing from the spirit of the invention.

F or example, the crude anthracene may be ground with a solvent for its oils but which does not dissolve other impurities such as phenanthrene or carbazole in considerable amounts; and these, or similar remaining impurities, may then be readily removed from the now finely ground anthracene by solvents or other treatments hereinbefore specified. Acetone or pyridine may also be used as the solvent with which to grind the crude anthracene, and will dissolve its oils, phenanthrene, carbazole, etc.; and these impurities when so rem'ovedcan then be separated from one another by well-known methods.

I claim l. The process of refining anthracene which includes grinding it in the presence of a solvent for impurities thereof in which the anthracene is relatively insoluble.

2. The process of refining anthracene which includes grinding it, in the presence of a solvent for impurities thereof in which the anthracene is relatively insoluble, for a period of one to two hours.

8. The process of refining anthracene which includes grinding it in the presence of a solvent for its oils in which the anthracene isrelatively insoluble.v

l. The process of refining anthracene which includes grinding it in the presence of a solvent for its oils in which the anthracene is relatively insoluble, removing the resulting solution, and then separating further impurities from the residue.

5. The process of refining anthracene which includes grinding it in the presence of a solvent for its oils and phenanthrene in which the anthracene is relatively insoluble.

, 6Q The process of refining anthracene which includes grinding it in the presence of a solvent for its oils and phenanthrene in which the anthracene is relatively insoluble, remov ing the resulting so1ution,,and then separating carbazole from the residue.

7 L The process of refining anthracene which includes grinding it in the presence ofa quail tity of carbon tetrachloride insufficient to dissolve anthracene in proportions relatively large to the impurities dissolved,and removing the resultant solution.

8. The process of refining anthracene which includes grinding one part of anthracene with V from one to two parts by weight of carbon tetrachloride, and removing the resultant so- I. lution.

9. The process of refining anthracene which includes grinding one part of anthracene with from one to two parts by weight of carbon tetrachloride, filtering the; mixture, washing 7 the remaining anthracene with'a further portion of the solvent, recovering the solvent and utilizing the same for subsequent operation. V

10. The process of refining anthracene V which includes grindingone part ofanthracene withfrom one to two parts by weight of carbon tetrachloride, filtering the mixture, washing the remaining anthracene with a further portion ofthe solvent, distilling off the solvent, and recovering the oils and phenanthrene. I 'Sign'edat New York in the county of New Yorkand'State of NewYork this 15th day of June A.D.1923.* V v CHARLES J. THATCHER. 

